2C-SNOW-PROFILE

The CloudSat Snow Proﬁle product (2C-SNOW-PROFILE) provides estimates of vertical proﬁles of snowfall rate along with snow size distribution parameters and snow water content for radar reﬂectivity proﬁles observed by the CloudSat Cloud Proﬁling Radar (CPR) which, based on an evaluation of the proﬁle and ancillary data, appear to coincide with snow at the surface. For these proﬁles, the product also estimates snowfall rate at the surface. Because of ground clutter, the CPR cannot reliably measure reﬂectivities near the surface. To overcome this limitation, the product algorithm estimates snow properties using a truncated reﬂectivity proﬁle, terminated somewhat above the surface, then uses the estimated snow properties in the bottom-most portion of the proﬁle to estimate the surface snowfall rate. For the truncated reﬂectivity proﬁle, proﬁles of size distribution parameters are retrieved using an optimal estimation algorithm which incorporates a priori information about snow microphysical properties, radar scattering properties, and size distribution parameters. Retrievals are performed only for proﬁles which appear likely to contain snow at the surface, either dry snow or snow with a small melted mass fraction. The retrieved size distribution parameter proﬁles and the a priori information are then used to calculate proﬁles of snowfall rates and snow water contents. The optimal estimation method produces uncertainty estimates for the retrieved size distribution parameters, and these uncertainties are then used to estimate uncertainties for the snowfall rates and snow water contents.

Control Frame 0, CPR Calibration
16: CPR to point in 160 seconds
17: CPR 15º to the right
18: CPR 15º to the left
19: CPR 10º to the right -- default rotation
20: CPR 10º to the left -- default rotation
21: CPR 5º to the right
22: CPR 5º to the left
23 - 29: Target ID for testing - not planned for operational use
30 - 36: CPR rotation - not planned for operational use
37 - 39: Not planned for operational use

Control Frame 1, Four thruster closed-loop
40: Rotation into the OR orientation
41: Rotation into the x-track along the anti-ang momentum
42: Rotation into the x-track along ang momentum
43: Rotation into the orbit lower orientation
44: Rotation into alt. OR w/ CPR away from Sun
45 - 49: Not planned for operational use

Control Frame 2, One thruster open-loop
50: Rotation into the OR orientation
51: Rotation into the x-track along the anti-ang momentum
52: Rotation into the x-track along ang momentum
53: Rotation into the orbit lower orientation
54: Rotation into alt. OR w/ CPR away from Sun
55 - 59: Not planned for operational use

Control Frame 3, Two thruster open-loop
60: Rotation into the OR orientation
61: Rotation into the x-track along the anti-ang momentum
62: Rotation into the x-track along ang momentum
63: Rotation into the orbit lower orientation
64: Rotation into alt. OR w/ CPR away from Sun
65 - 69: Not planned for operational use

Control Frame 4, Four thruster open-loop
70: Rotation into the OR orientation
71: Rotation into the x-track along the anti-ang momentum
72: Rotation into the x-track along ang momentum
73: Rotation into the orbit lower orientation
74: Rotation into alt. OR w/ CPR away from Sun
75 - 80: Not planned for operational use

Control Frame 5
81: Body into the x-track along the anti-ang momentum
82 - 1023: Not planned for operational use

The retrieved profile of log(lambda) for the precipitating column, where log() is common logarithm and lambda is the slope of the assumed exponential snow particle size distribution in mm^-1. The specified range is typical.

Estimated 1-sigma uncertainties for the retrieved profile of log(lambda) for the precipitating column, where log() is common logarithm and lambda is the slope of the assumed exponential snow particle size distribution in mm^-1. The specified range is typical.

Retrieved profile of log(N0) for the precipitating column, where log() is common logarithm and N0 is the intercept of the assumed exponential snow particle size distribution in m^-3 mm^-1. The specified range is typical.

Estimated 1-sigma uncertainties for the retrieved profile of log(N0) for the precipitating column, where log() is common logarithm and N0 is the intercept of the assumed exponential snow particle size distribution in m^-3 mm^-1. The specified range is typical.

A one-byte (8-bit) field for retrieval status flags. The following table gives the bit position and the condition indicated if that bit is set. The table starts from the least significant bit (position 0).

0: Snow detected in the profile
1: Snow detected at the surface
2: Retrieval completed but produced large chi-square value
3: The estimated snowfall rate at the base of the snow layer is substantially larger than that in the bin immediately above.
4: Required inputs from surface data are missing or in error
5: Required inputs from the profile data are missing or in error
6: Retrieval attempted and converged to invalid values
7: Retrieval attempted and failed to converge

Related News Articles

2016

CloudSat releases algorithm uncertainty study

September 1, 2016

The CloudSat algorithm development leads have completed a synthesis of algorithm uncertainties. The synopsis describes the known uncertainties in the Cloudsat algorithms and provides the relevant technical and peer reviewed references for data end-users. The algorithm development team plans to update the document periodically as new data releases become available.

2013

2C-SNOW-PROFILE released to the CloudSat Science Team

February 10, 2013

The CloudSat DPC has released to the CloudSat Science Team the R04 version of the 2C-SNOW-PROFILE (snow water content and snowfall rate) product. After a short review period of approximately two weeks the product will be released to the general science community.

All data users are asked to review the updated documentation available on the CloudSat DPC website. In addition, we ask that you report any anomalies or questions about the product to the DPC at cloudsat@cira.colostate.edu before the review period has ended.